Apparatus for reducing dye solutions



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ramadan. as, reas.;

ansatz FREDERIC A. EUSTIS, OF MILTON, MASSACHUSETTS.

APPARATUS FOR EID'UCING DYE SOLUTIOS.

@rlginalappllcation med November 17, 1921,`Seria1 No. 515,809. Dividedand this application led June It, 1922. Serial No. 568,164.

To all whom t may concer/n." l.

f. Be it known that l, FREDERIC A. lElUs'rIs, a citizen of the UnitedStates of America, and resident of Milton, in the county of, Norfolk andState of Massachusetts, have invented new and useful Improvements inApparatus for Reducing Dye Solutions, of which the following is aspecification.

The present application is a division of an application iled'by me Nov.17, 1921, Serial No. 515,809.

The principal object of the invention is to provide novel and improvedapparatus which effects important economies in the process, described insaid application, of reducing solutions whose utility in the artsrequires that they be used in a reduced state. Une of the chief uses towhich the invention is applicable is for reducing indigo dyes and othervat dyes, and by way of illustration l will therefore describe theapparatus and process as applied to the reduction of an indigo dyesolution, but it is to bennderstood that the invention is not limited tothe reduction of indigo, but is also applicable to the reduction ofother solutions.

To dye cloth or yarn with indigo, it has been customary to maintain asolution of rei duced indigo in one or more vats through which the cloth"or yarn is passed. The solution of indigo is absorbed by the cloth oryarn, and after the material'leaves the vat the indigo is oxidized byexposure to` the air, and is precipitated as an insoluble coloringmatter in the material. a

ln order to maintain the liquor in suitable condition for use it is'necessary to feed to it from\,.time to time proper quantities of indigopaste or dye and of a reducing agent,

,which reducing'agent may be supplied in` the form of a solid or liquid.-Suiicient re-V ducing agent must he added to thoroughly reduce theindigo' which is added, and also some further quantity to make good anyoxidation losses that occur during the process ot dyeing by reason ofoxidation on the surface or from oxygen which is carried into thesolution in the cloth or water or otherv agitator 7, consisting of apaddle or propel'- ler arranged near the bottom of the mixin wise.Sullicient reducing agents, particularly when in solution form, are ofconsiderable volume, and since there is nothing nor- `mally taken out otthe vat exceptin slight amount ot coloring matter whic adthe heres tothe cloth, the vats generally overflow or require to have a part of theliquor drawn od as a waste product to prevent overflow. rlhe cloth oryarn is usually introduced wet and is taken yout with about the samevolume of moisture, so that it neither adds much to nor'subtracts muchfrom the volume of liquor in the dye vat.

The reducing may be done with dry soto the liquor to be reduced, therebycausing voverflow and waste. Other reducingv agents are bulky and aregenerally less eicient, and give generally less good results. l l

With the present invention a reducing agent is produced in solution formand-is made in a part of the' dye solution or other' solution to bereduced, thereby securing the advantage of producing a hydros'ulphite insolution form, but eliminating the trouble,

waste and loss due to overflow or to anincrease in (volume of the liquorheretofore mentioned, and otherwise securing economies in the reductionof the dye solution.

rThe accompanying drawings illustrate diagrammatically apparatusembodying the invention, and adapted for `:arryingout .the said processwhich is claimed in my aforesaid application.

' Referring to the drawings, 1y represents a vat or vessel containingthe dye liquor or other solution to be treated. The solution is pumpedfrom the vat 1 by ,pump 2 through pipe 3 and pipe 4 controlled by valve5 into the mixing tank 6 where the, hydrosulphite solution is formed. lnythe rocess being described by way of illustration, this dyeing liquorconsists of a reduced indigo solution more or less oxidized by thedyeing process and other conditions ot its use. An

tank and driven by -a shaft 8, is then starte and there is added to theliquor in the mix- 1n tank a suitable uantity of zinc dust. Utlierpowdered meta ssuch as iron might los be used but` powdered zinc `i spreferable. The reactions Which take place inthe mixing tank generateheat and in order to` avoid overheating the solution, -the mixing tank 6is cooled by a Water jacket 9l or by cooling coils 10, or both. 'llhereis then introduced into the mixing-tank a suitable quantity of ing tankis measured either ,by Weight or by .volume in the measuring tank 13.lli the sulphur dioxide is to be measured by Weight, the tank 13 Will bemounted on scales; if it is to be measured by volume the tank 13 may beprovided with a gauge glass 16 With which is associated a suitablemeasuring' scaleto indicate the quantities contained in the tank atvarious levels.

A uniform flow of sulphur dioxide into the mixing tank 6 is, secured bypassing it from the bottom of the measuring tank 13 through a short pipeor hose 17 which is made of such proportions that the loss of headcaused by the How of the liquid through the pipe 17 at the desired` rateWill balance the pressure in the measuring tank, whichv pressure is afunction of the temperature of the roo'm. The connection 17 iscontrolled by a valve 18 at the bottom of tank :13. ln case the pressurein tank 13 becomes excessive, it may be reduced b v opening the `valve20 in a Joy-pass pipe 19, and closing the valve 18, which allows theescape of gas through pipes 19 and 17, thus directly re-l lieving thepressure in tank 13 und also reducing the. temperature and consequentlythe pressure in tank 13 by the volatilizatiou resulting from opening thebypass 19. The sulphur dioxide is introduced through pipe 17 near thepoint in the mixing tank. Where the agitation'ot the solution is mostactive. The vzinc or other metallic dust is kept in suspension in thesolution by the action of the agitator and the sulphur dioxide as itenters meets a swirling mass of zinc dust and liquid so that no excessof sulphur dioxide will occur at any point.

The sulphur dioxide reacts with the Zinc dust in the dye liquor andforms lirst zinc hydrosulphite. This probably reacts at once With anyunreduced indigo in the solution.

After the sulphur dioxide is all introduced a suitable quantity ofalkali such as caustic soda or carbonate of sodium is added to themixing tank to convert the zinc hydrosulplnte and other zinc saltspresent -into nasa-15a sodium salts, and also to hold the indigo insolution. rlhe dye liquor often contains an excess of caustic alkaliwhich should be taken into account. in. determining the amount ofcaustic alkali to be added.` The caustic soda or carbonate of sodium orother alkali may, if desired, be put directly into the mixing tank indry form and there taken into solut1on. rlhe solution of the causticalkali yliberates a considerable quantity oi heat, but the cooling coilsand Water jacket Will be made ample to absorb this.

Instead of introducing the alkaline agent dry into the mixing tank itmay, if preferred, be introduced in solution. To this end a suitabletank 21 is provided in Which the alkaline agent is dissolved in part ofthe dyeing solution supplied from vat l through pipe 3 and pipe 24:controlled by valve 25. The alkaline solution is delivered inthe desiredquantity to the mixing tank 6 from tank 21 through pipe y22 controlledby valve 23.

As the alkali is added the Zinc is precipitate-d. The solution in themixing tank 6 is then forced through pipe 26 cont-rolled by valve-26 bymeans'of a pump 27 into a iilter press 28 which may be of usual orsuitable form, and from the filter press 28 the clear solution carryingan excess of the reducing agent with the indigo all thoroughly reduced,is run by pipe 29 into a storage tank 30. v

Since the precipitate retained in the filter press Wil-l contain a smallamount of available reducing solution, a further part of thc dye liquormay be pumped from the dye vat 1 through the mixing tank 6 and throughthe filter press 28 to Wash these precipitates.

Il`his liquor Will absorb substantially the last traces of the reducingagent. It may be followed by a small quantity oi Water merely sulicientto replace the solution retained by the precipitate. The press mayy thenbe cleaned and set up ready for the next run.

The reducing solution collected iu the storage tank 30 may then be usedin two ways. Part of it may be run directly into the dye vat 1 throughpipe 31 controlled by valve 32.l Part of it may be run into the indigomixing tank 33 through pipe 34 controlled by valve 35. ln the indigomixing tank 33 suitable quantities of fresh indigo paste or dye areadded together with suitable quantities of caustic soda. Theseingredients when thoroughly mixed Will then be passed through pipe 36controlled by valve 37 into the dye vat 1.

As an alternative procedure, the storage tank 30 and the indigo mixingtank 33 might be omitted and the solution delivered direct from themixing tank 6 through the filter press 28 into the dye vat 1. 1n thisevent the required additional quantities of indigo paste and of causticmay be added in the lil mixing tank 6 after the hydrosulphite solutionis formed with sulphur dioxide and zinc dust, or the indigo paste andthe caustic might be added directly in the dye vat l, caustic beingsupplied, it desired, from the tank 2l through pipe 38 controlled byvalv'e 39.

lV ith the foregoing apparatus and process a part ot the solution itselfwhich is tobe reduced is brought in contact with the hydrosulphite whilethelatter is being produced;

that is, the hydrosulphite is manufactured with sulphur dioxide and zincdust or its equivalent directly in a part ot the solution to be reducedby it, thus avoiding oxidation and Waste, and making it possible to useliberal quantities of solution from the dye vats and thereby to Workwitha solution of convenient dilution Without the disadvantage ot increasingthe volume ot the dye liquor and thereby necessitating either tht wasteof a partot the liquor or a treatmentof it by an expensive reclaimingprocess. Moreover, the apparatus and process described minimizes themechanical handling of the solutions and salts and makes possible aprocedure on a large scale With a minimum cost for labor.

The combination of the use of the dye liquor and liquid sulphur dioxidein conjunction with Zinc or other suitable metal for the production ofhydrosulphite solutions of reducing agents, has an especial advantagebecause the liquid sulphur dioxide is easily available in a very purecondition and carries into the dye 'liquor a minimum ot' impurity,Whereas the introduction ot sodium bisulphite for example in/tn the dye.liquor -tor the production ot a reducing solution is undesirablebecause with sodium bisulphite there is introduced so much soluble saltsas to be detrimental to the dyeing proc ess and to render the same.impracticable.

l claim:

l. Apparatus for reducing solutions comprising a vat, a mixing tank,means to deliver solution :trom the vat to the mixing tank, a sulphurdioxide supply tank, means to deliver sulphur dioxide from the supplytank to the mixing tank, a lilter, means to deliver solution fromthemixing tank to the filter 'and means to deliver filtered solutionfrom the tilterfto the vat.

2. Apparatus for reducing dye solutions comprising a dye vat, a mixingtank, means to deliver solution from the dye vat to theA mixing tank, afilter, means to deliver solution from the mixing tank to the lter, astorage tank,'means to deliver liltered solution from the -lilter to thestorage tank, a dye mixing tank, means to deliver solution from thestorage tank to the dye mlxing tank, means to deliver -solution from thestorage tank to the dye vat, and means to deliver solution from the dyemixing tank to the dye vat.

8. Apparatus for reducing solutions com- 'rrisino' a vat a mixinw tankmeans to deliver solution from the vat to the mixing tank, a sulphurdioxide supply tank, means to deliver sulphur dioxide from the supplytank to the mixing tank, an alkali tank, means to deliver solution fromthe vat to the alkali tank, means to deliver alkali solution from thealkali tank to the mixing tank, a filter, means to deliver solution fromthe mixing tank to the filter, and means to de liver filtered solutionfrom the filter to the vat.

4. Apparatus for reducing dye solutions comprising a dye vat, a mixingtank, means to deliver solution from the dye vat to the mixing tank, asulphur dioxide supply tank,

'means to deliver sulphur dioxide from the supply tank to the mixingtankyan alkali tank, means to deliver solution from the dye vat to thealkali tank, means to deliver .alkali solution trom the alkali tank tothe FREDERC A. EUS'lllS.

